Primobolan aka Methenolone Enanthate is a dihydrotestosterone (DHT) based anabolic steroid. It is an ester derivative of methenolone sold commonly under the brand names Primobalan (tablet form) or Primobolan (injectable).
When it interacts with the aromatase enzyme it does not form any estrogens. It is used by people who are very susceptible to estrogenic side effects, having lower estrogenic properties than nandrolone. Methenolone, in form of enanthate and acetate, is available as an injection or as an oral respectively.
The injection is naturally regarded as having a higher bioavailability. It is an enanthate ester which is quite long-acting. Because it by-passes hepatic breakdown on the first pass, it also has a higher survival rate. The tablets are in a short-lived acetate form. Methenolone is not 17-alpha-alkylated, but 1-methylated for oral bioavailability. This reduces the stress on the liver. It is considered one of the safer steroids, meaning it has few side effects. Methenolone has no estrogenic side effects, and its effects on cholesterol levels are minimal.
Methenolone is also not overly suppressive of the HPTA axis, although how suppressive is debatable. For this reason, many bodybuilders use it in between steroid cycles during their “off-time” to help maintain their gains and strength.